一种改进的基于峰值信噪比-高阶奇异值分解的天波超视距雷达自适应海杂波抑制算法

天波超视距雷达(OTHR)舰船目标的检测性能受目标区海杂波的影响严重,准确且自适应的海杂波抑制效能对改善低可探测舰船目标的检测性能意义重大。该文针对基于高阶奇异值分解(HOSVD)的海杂波抑制算法非自适应机制的不足,通过引入峰值信噪比(PSNR),提出一种改进的基于PSNR-HOSVD的自适应算法。该算法仅利用第3等效模式展开矩阵的左奇异向量构造一个投影矩阵,相比于HOSVD算法,该文算法可有效降低计算复杂度,同时由于海杂波仅在第3等效模式展开矩阵的列空间中具有聚集特性,因此该文算法具有比HOSVD算法更好的海杂波抑制性能。实测数据处理结果表明,在电离层状态理想和非理想的情况下,该文PSNR-HOSVD自适应算法的性能均优于EVD自适应算法和HOSVD非自适应算法。     

OTHR短CIT条件下自适应舰船目标检测方案

针对在短相干积累时间（CIT）条件下,天波超视距雷达（OTHR）的多普勒频率分辨力和相干积累处理增益降低,导致对低可探测大中型舰船目标检测性能下降的问题,提出一种综合自适应海杂波抑制、重构并检测舰船目标信号的PHM方案。该方案首先利用峰值信噪比（PSNR）-高阶奇异值分解（HOSVD）算法进行自适应海杂波抑制,使信号稀疏化并减少后续检测环节中的虚警;然后利用改进的正交匹配追踪（MOMP）算法进行重构和检测舰船目标信号,改善对目标的检测性能,并提升检测结果中舰船目标的多普勒频率准确度。仿真分析和实测数据处理结果验证了PHM方案的有效性。      

基于回声状态网络的OTHR海杂波抑制方法

在短相干积累时间(CIT)情况下,天波超视距雷达(OTHR)中低速目标检测很困难:低速目标靠近强大的海杂波频谱;短CIT导致多普勒分辨率低,使目标信号与海杂波更难区分。传统方法一般利用海杂波与目标信号的时频特征不同来抑制海杂波,目标速度较高时这些方法很有效,然而在短CIT、低速目标情况下目标与海杂波信号的时频特征的区分度很小,使得传统方法难以有效抑制海杂波。针对上述问题,考虑到海杂波与目标信号具有不同的动力学特征,提出一种基于回声状态网络的天波雷达海杂波抑制方法。该方法首先用海杂波参考信号训练回声状态网络,使该神经网络"记住"海杂波的混沌动态特征;然后用前述训练好的网络重构和预测天波雷达回波中...     

基于奇异值分解的空域海杂波抑制算法

为实现对高频地波雷达(high frequency surface wave radar, HFSWR)一阶海杂波谱中目标的检测,提出了基于奇异值分解(singular value decomposition, SVD)的空域海杂波抑制算法（简称空域SVD算法）. 空域SVD算法是利用海杂波较强的相关性,将邻近距离单元作为参考,对其阵列协方差矩阵进行SVD,估计空域的海杂波子空间和噪声子空间;再利用子空间的正交性,从阵列回波信号中去除其在海杂波子空间的投影分量,达到在空域抑制海杂波的目的. 该方法与现有的空域海杂波抑制方法相比,不需要预先知道海杂波的方位,利用阵列协方差矩阵的SVD来估计子空间,使得子空间的估计比较容易且准确,提高了输出信杂噪比(signal to clutter plus noise ratio, SCNR),有利于目标的检测.     

基于信号阻塞矩阵检测OTHR舰船目标

为了提高天波超视距雷达目标检测效能,实战中要求在短相干积累条件下检测舰船目标。但是短相干积累时间会导致回波谱的多普勒分辨率降低,增加从强大的海杂波中检测出舰船目标的难度。针对这一问题,提出了一种基于信号阻塞矩阵检测海面舰船目标的新方法。该方法通过构造阻塞矩阵对海杂波进行抑制,使舰船目标最终显现出来。与传统的Root海杂波迭代对消法相比较,新方法不需要估计信号的幅度和初相,缩短了计算时间,减小了估计误差,且能在低信噪比或目标多普勒频率靠近一阶Bragg峰的情况下获得更佳的目标检测性能。以上结论和比较得到了模拟和实测数据的验证。     

修正Hankel矩阵SVD用于多模环境杂波对消研究

针对超视距雷达多模传播下杂波展宽导致的慢速目标掩盖问题,直接在多模情况下进行杂波对消与目标检测。分析了基于Hankel矩阵奇异值分解(SVD)的海杂波对消方法,指出了该方法存在的不足,并通过设置判决门限进行修正。实验结果显示,采用基于修正的Hankel矩阵SVD的海杂波对消技术,能够实现对目标的检测。     

基于TBD技术的高频雷达舰船目标检测

针对强海杂波背景下高频雷达的舰船目标检测问题,提出了基于检测前跟踪(TBD, track before detect)技术的检测方法.该方法先在多普勒域对回波数据进行杂波抑制和低门限CFAR(constant false alarm rate)预处理以降低虚警率和计算复杂度,再采用动态规划TBD算法进行检测和跟踪以提高检测性能.蒙特卡洛仿真结果和回波数据验证表明该方法可提高对一阶海杂波附近舰船目标的检测能力,工程实用性强.     

基于灰度相关性的SAR图像联合CFAR舰船检测算法

分析了中高分辨率SAR海洋图像的目标和海杂波特点,利用了SAR海洋图像中舰船目标的灰度相关性、形状特性以及舰船目标与背景杂波的信杂比特性,提出了一种基于灰度相关性的联合CFAR舰船检测算法。算法综合利用了舰船目标内部相邻像素间的灰度强相关性和舰船目标和海杂波的信杂比,建立了海杂波区域内相邻像素间灰度值的二维对数正态分布来实现联合CFAR检测。该算法能够改善斑点噪声和背景局部不均匀对检测带来的虚警,检测效果相比于传统检测算法更加优越。     

天波雷达电离层污染校正与海杂波抑制

在天波超视距雷达（OTHR）中,舰船目标的多普勒频率与海杂波谱接近,电离层污染会导致海杂波频谱展宽,从而淹没邻近的舰船目标信号。考虑到电离层污染会导致OTHR回波信号的相位缓慢变化,提出了采用相位梯度法对回波信号进行电离层污染校正;利用污染校正后的海杂波可以近似为两个单频信号之和这一特点,提出了应用奇异值分解来实现对海杂波的抑制。仿真结果表明,文中算法可以有效地校正电离层污染,抑制海杂波,显著提高信杂比,从而有效解决强海杂波对舰船目标的遮蔽问题。与现有的HRR—SVD算法相比,文中算法可以适用于相干积累时间较长和电离层污染较大的情况,防止残留的海杂波形成虚警,提高了OTHR对海杂波附近舰船目标的检测能力。     

短相干积累条件下天波超视距雷达的舰船检测

天波超视距雷达(OTHR)的观测范围非常广,实战中经常要求在短相干积累条件下检测出舰船目标。然而短相干积累时间带来的低多普勒分辨率很难从强大的海杂波中区分出舰船。为了解决这一问题。可以采用海杂波循环对消法,这就要求对杂波参数进行精确估计。传统方法直接利用Fourier谱中的最大幅度估计杂波参数,估计精度不高从而导致对消性能不太理想。该文提出了一种新的基于FFT相位分析的杂波对消法。该方法与传统的杂波对消相比,有效提高了参数估计精度,减小了剩余杂波强度和扩散程度,有利于舰船目标的峰值显露和从剩余杂波中区分出舰船。以上分析和比较得到了实测数据的检验。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.